Add contributor entry for @helderco
Add contributor entry for @helderco

For #6713

gasman/wagtail,rsalmaso/wagtail,zerolab/wagtail,kaedroho/wagtail,zerolab/wagtail,jnns/wagtail,thenewguy/wagtail,rsalmaso/wagtail,torchbox/wagtail,thenewguy/wagtail,wagtail/wagtail,kaedroho/wagtail,zerolab/wagtail,kaedroho/wagtail,torchbox/wagtail,torchbox/wagtail,mixxorz/wagtail,kaedroho/wagtail,zerolab/wagtail,wagtail/wagtail,jnns/wagtail,mixxorz/wagtail,zerolab/wagtail,wagtail/wagtail,gasman/wagtail,kaedroho/wagtail,jnns/wagtail,gasman/wagtail,gasman/wagtail,jnns/wagtail,thenewguy/wagtail,mixxorz/wagtail,wagtail/wagtail,torchbox/wagtail,thenewguy/wagtail,rsalmaso/wagtail,gasman/wagtail,mixxorz/wagtail,rsalmaso/wagtail,mixxorz/wagtail,wagtail/wagtail,rsalmaso/wagtail,thenewguy/wagtail